Such folding bench seats are intended to offer an opportunity of comfortable seating for passengers, and during overnight stays or pauses is intended to be foldable into a position which forms as wide and comfortable as possible a reclining surface for at least one person. Also however these folding bench seats should take account of the increased safety requirements of modern caravans. Thus the previous two-point restraint system is increasingly being replaced by the three-point belt system, which in the case of an accident provides clearly improved protection for the occupants. The incorporation of three-point restraint systems requires the presence of a stable structure, which however is often not present in caravans. Therefore as a rule an upright column is located on the seat back, which is attached to the floor/frame area of the vehicle, and ensures sufficient stability for the attachment of upper connection points for three-point restraint systems.
The document DE-U-93 14 859 (=DE-A-43 33 420) describes such a folding bench seat with restraint system for caravans. This folding bench seat substantially consists of a frame structure, into which there is integrated a belt bearer, an upright column, upon which there is located an upper connection point for a three-point restraint system, a back unit and a seat unit. The upright column is inserted into a complementary recess in the belt bearer and secured in an upright position therein. Thus the restraint system, starting from the belt bearer, is passed through the column, in the form of a cavity profile, to the upper connection point of the upright column in an upward direction. Furthermore, the seat back and seat surface are secured in a foldable manner on the frame construction, so that the latter, in the unfolded position, together with a folding bench seat of similar structure, form a larger reclining surface.
A considerable disadvantage of this construction of folding bench seat however is that on its own it does not form a reclining surface which is sufficiently long and large to serve as a sleeping place for several persons, so that cooperation with another similar bench seat arrangement is always necessary. A further considerable disadvantage of this column arrangement resides in the fact that the belt forces occurring in an accident are absorbed by the upright column alone, which is thus subjected to intense bending stress. Therefore, under the effect of the bending moment resulting from this type of introduction of force, considerable tension peaks occur at the anchoring point of the column in the frame. This also applies to seat columns which are foldably mounted according to DE-A-44 42 813, as in this case the column, due to its length, is exposed to intense bending stresses in a crash situation. In addition, this construction requires a considerable amount of space for folding, which is however often taken up by assemblies on the rear side of the folding bench seat. This can lead to considerable restrictions in the use of the living or lying surface, or to a risk of injury on the relatively sharp-edged column.